I noticed when compating v1.29.2 windows-x64 Syncthing.exe to v1.29.4, that the certificate changed. We previously had “Stifelsen Syncthing” and now it’s “Kastelo AB”.
The Stiftelsen Syncthing certificate expired, so needed a replacement. I did ask @calmh about the new Kastelo AB (which is now a very shortlived cert) a while ago, and yeah I got confirmation back that this is the new signer (from Microsoft’s cloud it seems, so likely a service and not a purchased certificate per-se).